“add to set” returns a boolean in java - what about python?

Question

In Java I like to use the Boolean value returned by an \"add to the set\" operation to test whether the element was already present in the set:

if (set.add(\         


        

Answer 1

Generally, Python tries to avoid using conditions with side-effects. That is, the condition should be just a test, and operations that change data should happen on their own.

I agree that it's sometimes convenient to use a side-effect in a condition, but no, in this case, you need to:

z = set()
if y not in z:
    z.add(y)
    print something

Personally I like the simple expressiveness of if y not in z:, even if it takes up one more line of code, and it's one less thing to mentally parse when reading the the code at a later date.